Index: source/tools/i18n/checkTranslationsFontTags.py
===================================================================
--- source/tools/i18n/checkTranslationsFontTags.py
+++ source/tools/i18n/checkTranslationsFontTags.py
@@ -0,0 +1,74 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2021 Wildfire Games.
+# This file is part of 0 A.D.
+#
+# 0 A.D. is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#
+# 0 A.D. is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
+
+import os, re, sys
+from tqdm import tqdm
+from tqdm import trange
+
+def checkTranslationsFontTags(inputFilePath, fontPatterns):
+    with open(file=inputFilePath,mode="r",encoding="utf-8") as file:
+        data = file.read()
+        found = False
+        subErrors = set()
+
+        for fontPattern in fontPatterns:
+            matches = list(fontPattern.finditer(data))
+            if len(matches) > 0:
+                for match in matches:
+                    if match is not None:
+                        subErrors.add("\t" + match.group(1))
+                        found = True
+
+        if found == False:
+            return
+
+        return inputFilePath.replace("../","") + ":\n" + "\n".join(subErrors)
+
+def main():
+    fontPatterns = [
+        # Explanation of the monster below. Some translators
+        # replace programmer's quotes by quotes from their languages which is
+        # generally fine for text but breaks font tags. They also sometime add spaces
+        # Anything that's not  [font=\"something\"] [/font] is incorrect.
+        # We also have a broken example:
+        # "Epibátēs Athēnaîos [font="sans-bold-16"](Athenian Marine)[/font]"
+        re.compile(r"\n(.*(?!(\[font=\"sans-bold-16\"\]))(?!(\[font=\\\".*\"\]))\[(?:\s+)?font(?:\s+)?=(?:\s+)?(?:[^(\"|\\)]|(?:\\|\")).*(?:[^(\"|\\)]|\")(?:\s+)?\]).*\n", re.IGNORECASE),
+        re.compile(r"\n(.*(?!(\[\/font]))\[(?:\s+)?\/(?:\s+)?font(?:\s+)?\])", re.IGNORECASE),
+    ]
+
+    errors = []
+    listOfFiles = os.walk("../../../binaries/data/")
+    flatFileList = []
+    for root, _, filenames in listOfFiles:
+        for filename in filenames:
+            if ".po" in filename:
+                flatFileList.append(os.path.join(root,filename))
+
+    for filename in tqdm(flatFileList):
+        try:
+            error = checkTranslationsFontTags(filename, fontPatterns)
+            if error is not None:
+                errors.append(error)
+        except:
+            print("Error parsing: " + filename)
+
+    if len(errors):
+        print("Found errors in the following files: \n" + "\n".join(errors))
+
+if __name__ == "__main__":
+    main()